linux-kernel - Re: [PATCH] usb: dwc3: Always deassert xilinx resets

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Message-ID: <20260109004901.ygts6mmcxy4vs3y2@synopsys.com>
Date: Fri, 9 Jan 2026 00:49:03 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Sean Anderson <sean.anderson@...ux.dev>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "open list:DESIGNWARE USB3 DRD IP  DRIVER" <linux-usb@...r.kernel.org>,
        Neal Frager <neal.frager@....com>, Michal Simek <michal.simek@....com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/ZYNQ ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Radhey Shyam Pandey <radhey.shyam.pandey@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] usb: dwc3: Always deassert xilinx resets

On Tue, Jan 06, 2026, Sean Anderson wrote:
> If we don't have a usb3 phy we don't need to assert the core resets.
> Deassert them even if we didn't assert them to support booting when the
> bootloader never released the core from reset.
> 

> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
> ---
> 
>  drivers/usb/dwc3/dwc3-xilinx.c | 67 ++++++++++++++++------------------
>  1 file changed, 32 insertions(+), 35 deletions(-)
> 

This sounds like a fix. Does it need to be Cc Stable and backported?

Regardless,

Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

Thanks,
Thinh

> diff --git a/drivers/usb/dwc3/dwc3-xilinx.c b/drivers/usb/dwc3/dwc3-xilinx.c
> index 0a8c47876ff9..f41b0da5e89d 100644
> --- a/drivers/usb/dwc3/dwc3-xilinx.c
> +++ b/drivers/usb/dwc3/dwc3-xilinx.c
> @@ -132,21 +132,6 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
>  		goto err;
>  	}
>  
> -	/*
> -	 * The following core resets are not required unless a USB3 PHY
> -	 * is used, and the subsequent register settings are not required
> -	 * unless a core reset is performed (they should be set properly
> -	 * by the first-stage boot loader, but may be reverted by a core
> -	 * reset). They may also break the configuration if USB3 is actually
> -	 * in use but the usb3-phy entry is missing from the device tree.
> -	 * Therefore, skip these operations in this case.
> -	 */
> -	if (!priv_data->usb3_phy) {
> -		/* Deselect the PIPE Clock Select bit in FPD PIPE Clock register */
> -		writel(PIPE_CLK_DESELECT, priv_data->regs + XLNX_USB_FPD_PIPE_CLK);
> -		goto skip_usb3_phy;
> -	}
> -
>  	crst = devm_reset_control_get_exclusive(dev, "usb_crst");
>  	if (IS_ERR(crst)) {
>  		ret = PTR_ERR(crst);
> @@ -171,22 +156,31 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
>  		goto err;
>  	}
>  
> -	ret = reset_control_assert(crst);
> -	if (ret < 0) {
> -		dev_err(dev, "Failed to assert core reset\n");
> -		goto err;
> -	}
> +	/*
> +	 * Asserting the core resets is not required unless a USB3 PHY is used.
> +	 * They may also break the configuration if USB3 is actually in use but
> +	 * the usb3-phy entry is missing from the device tree. Therefore, skip
> +	 * a full reset cycle and just deassert the resets if the phy is
> +	 * absent.
> +	 */
> +	if (priv_data->usb3_phy) {
> +		ret = reset_control_assert(crst);
> +		if (ret < 0) {
> +			dev_err(dev, "Failed to assert core reset\n");
> +			goto err;
> +		}
>  
> -	ret = reset_control_assert(hibrst);
> -	if (ret < 0) {
> -		dev_err(dev, "Failed to assert hibernation reset\n");
> -		goto err;
> -	}
> +		ret = reset_control_assert(hibrst);
> +		if (ret < 0) {
> +			dev_err(dev, "Failed to assert hibernation reset\n");
> +			goto err;
> +		}
>  
> -	ret = reset_control_assert(apbrst);
> -	if (ret < 0) {
> -		dev_err(dev, "Failed to assert APB reset\n");
> -		goto err;
> +		ret = reset_control_assert(apbrst);
> +		if (ret < 0) {
> +			dev_err(dev, "Failed to assert APB reset\n");
> +			goto err;
> +		}
>  	}
>  
>  	ret = phy_init(priv_data->usb3_phy);
> @@ -201,11 +195,15 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
>  		goto err;
>  	}
>  
> -	/* Set PIPE Power Present signal in FPD Power Present Register*/
> -	writel(FPD_POWER_PRSNT_OPTION, priv_data->regs + XLNX_USB_FPD_POWER_PRSNT);
> -
> -	/* Set the PIPE Clock Select bit in FPD PIPE Clock register */
> -	writel(PIPE_CLK_SELECT, priv_data->regs + XLNX_USB_FPD_PIPE_CLK);
> +	if (priv_data->usb3_phy) {
> +		/* Set PIPE Power Present signal in FPD Power Present Register*/
> +		writel(FPD_POWER_PRSNT_OPTION, priv_data->regs + XLNX_USB_FPD_POWER_PRSNT);
> +		/* Set the PIPE Clock Select bit in FPD PIPE Clock register */
> +		writel(PIPE_CLK_SELECT, priv_data->regs + XLNX_USB_FPD_PIPE_CLK);
> +	} else {
> +		/* Deselect the PIPE Clock Select bit in FPD PIPE Clock register */
> +		writel(PIPE_CLK_DESELECT, priv_data->regs + XLNX_USB_FPD_PIPE_CLK);
> +	}
>  
>  	ret = reset_control_deassert(crst);
>  	if (ret < 0) {
> @@ -225,7 +223,6 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
>  		goto err;
>  	}
>  
> -skip_usb3_phy:
>  	/* ulpi reset via gpio-modepin or gpio-framework driver */
>  	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
>  	if (IS_ERR(reset_gpio)) {
> -- 
> 2.35.1.1320.gc452695387.dirty
>